New set up of an old boiler with storage

[nbrouse]

So ive been attempting to dig around on here to find some answers but maybe im just not good at navigating the forum so im going to do the newbie thing and make a thread.

Ive got a tarm mb solo 40 built in 2000 and in good shape i picked up used. I want to build a diy thermal storage tank. Im currently scouring for the best plans. Going pressurized isnt really an option due to where it will be. As for emitters i plan to tie this into my exisiting forced air set up that heats and cools my whole house via heat pump and elec furnace back up at the moment.
Im heating about 1400 sq foot 1 story home freshly remodeled (some still in process) with new insulation and windows all around. In southern Pennsylvania.



The boiler itself is in good shape and ive got 25 years experience operating a conventional wood boiler heating my parents house growing up and a few properties of my own over the years. The boiler will be in a 12x12 room i built off the back of my house lined with 5 inches of spray from on all sides and the ceiling. It gets toasty in there with the current forced air stove.

The storage tank i want to build will be about 25 feet a way in the basement of my house where 2 soon to be removed oil tanks sit. I plan to build with a nominal size of 4x8x4 leaving me in the ball park of 700-800 gallons depending on insulation set up. The questions i have for the storage side as this is new to me.

1- epdm liner vs sanitred. Epdm seems proven albeit maybe a 10 year window. I can live with that. Sanitred intrigues me but i cant find many ppl with experience.

2 - has anyone used a hx coil pressurized on the boiler side to heat the storage or do is it always non pressurized with a feed and return? What are the pros and cons?

3 - on the emitter side it will be closed loop running a 12x18 air to water exhange in the plenum of my air handler and i am considering adding a cast iron radiator in my master bedroom. Is that considered i guess i would need an expansion tank on that side as that would be pressurized correct?

4 - storage tank again. I found some plans from a solar site someone on here referenced and it was plywood and 2x4s. Has anyone considered fiberglass sheets? We have a fiberglass manufacturer locally and i can source "2nds" that have esthetic blemishes. I was thinking maybe 3/8 or 1/2 inch sheets of fiberglass instead of plywood. Would i be crazy to use that and silocone the joints? Or maybe still use a liner of sorts?

5 - what size pipe should i run on either side of the storage tank?

Id appreciate any kind of feed back. Im looking to get this kit up and running in the next 4 weeks or so. Im accumulating parts as we speak.

Thanks

 

[peakbagger]

IMO the best non pressurized thermal storage tank that could be built on site (carried through doors and stairs) is a Heat Bank made by a Hearth.com member Tom in Maine. He is no longer building them and the business is for sale. https://www.americansolartechnics.com/heat-bank-storage-tanks.html. It is a great design made out of Isoboard foam roofing with sheetmetal reinforcing. The tricky part is the liner which is an issue with most homemade tanks. He used a custom welded PVC liner (that he welded). He tried several other materials including EPDM and they did not hold up. Do not let anyone convince you that EPDM based systems will work, he tried a couple of alternative materials they are not rated for continuous immersion at elevated temperatures and they failed prematurely. He went back to welded PVC. His design also had a large heat exchanger, mine is copper but I think he went to stainless in the later years. His design is a flexible liner, others have tried concrete tanks with some sort of coating system.

His system used an internal coil (or two if someone wanted domestic water. Once the tank is filled the water is there until its drained, although since its vented due to expansion and contraction of the water, it does need to be topped up on occasion. My wood boiler heats the coil which heats the tank water and then when there is a call for heat, the same coil is used to pull heat out of the tank.

Note on tank materials, the issue is with elevated temperatures, if you have standard radiators, they were most likely sized for 160 to 180 F water, therefore you need to run your storage up to 180 F. If you try to run at lower temps in the baseboards it will work for some of the year but when it gets real cold out you will be short on radiators and have trouble heating the house. Storage volume is function of capacity and temperature. If you have properly designed radiant heat or modern low temperature radiant emitters than you can heat your house with 80 F water. In that case, the effective storage volume can be lot smaller as the system can use all the heat from 180F down to 80 F while using standard baseboard you can only use the heat from 180 to 160 before you start losing out on heating capacity. Effectively your storage for the low temp system can be 1/5 the size. A wood boiler can put out 200 F water so the temptation is run the storage hotter but if you use a resilient liner its not going to last.

Unless you go with very expensive industrial resins, fiberglass has the same issues with temperature in immersion service so be very careful in getting specs and guarantees on the continuous immersion rating. The best resin I am aware of it Novalac and that is rated for 200F max immersion temp.

Years ago I had a stainless steel industrial tank lined with a Stonehard industrial coating that was rated at higher temps but I have no idea what particular product it was.

I can sympathize with you on the storage, I am considering building a new house and expect I will go with insulated stainless IBC totes that will go in the basement when the house is built unless Tom finds a buyer for his business. I will build a coil that goes into the manway on top and stick with unpressurized system. Plenty of folks use propane tansk for pressurized systems and they are happy with them but I will let them convince you.

 

[nbrouse]

IMO the best non pressurized thermal storage tank that could be built on site (carried through doors and stairs) is a Heat Bank made by a Hearth.com member Tom in Maine. He is no longer building them and the business is for sale. https://www.americansolartechnics.com/heat-bank-storage-tanks.html. It is a great design made out of Isoboard foam roofing with sheetmetal reinforcing. The tricky part is the liner which is an issue with most homemade tanks. He used a custom welded PVC liner (that he welded). He tried several other materials including EPDM and they did not hold up. Do not let anyone convince you that EPDM based systems will work, he tried a couple of alternative materials they are not rated for continuous immersion at elevated temperatures and they failed prematurely. He went back to welded PVC. His design also had a large heat exchanger, mine is copper but I think he went to stainless in the later years. His design is a flexible liner, others have tried concrete tanks with some sort of coating system.

His system used an internal coil (or two if someone wanted domestic water. Once the tank is filled the water is there until its drained, although since its vented due to expansion and contraction of the water, it does need to be topped up on occasion. My wood boiler heats the coil which heats the tank water and then when there is a call for heat, the same coil is used to pull heat out of the tank.

Note on tank materials, the issue is with elevated temperatures, if you have standard radiators, they were most likely sized for 160 to 180 F water, therefore you need to run your storage up to 180 F. If you try to run at lower temps in the baseboards it will work for some of the year but when it gets real cold out you will be short on radiators and have trouble heating the house. Storage volume is function of capacity and temperature. If you have properly designed radiant heat or modern low temperature radiant emitters than you can heat your house with 80 F water. In that case, the effective storage volume can be lot smaller as the system can use all the heat from 180F down to 80 F while using standard baseboard you can only use the heat from 180 to 160 before you start losing out on heating capacity. Effectively your storage for the low temp system can be 1/5 the size. A wood boiler can put out 200 F water so the temptation is run the storage hotter but if you use a resilient liner its not going to last.

Unless you go with very expensive industrial resins, fiberglass has the same issues with temperature in immersion service so be very careful in getting specs and guarantees on the continuous immersion rating. The best resin I am aware of it Novalac and that is rated for 200F max immersion temp.

Years ago I had a stainless steel industrial tank lined with a Stonehard industrial coating that was rated at higher temps but I have no idea what particular product it was.

I can sympathize with you on the storage, I am considering building a new house and expect I will go with insulated stainless IBC totes that will go in the basement when the house is built unless Tom finds a buyer for his business. I will build a coil that goes into the manway on top and stick with unpressurized system. Plenty of folks use propane tansk for pressurized systems and they are happy with them but I will let them convince you.

i appreciate the feedback.
a pressurized system storage tank is out of the question for me unfortunately. i dont have a good place to put one outside and i cannot fit what i would need into my basement. so i am definitely going to be building an unpressurized storage tank. it is really just a matter of what liner i use. i did try to access toms site and unfortunately found it wasd out of business so im likely going to be going with the rubber liner.

however you mention you have one closed loop system that heats your tank and your emitters. this is something i have seen different variations of and i would prefer this set up. i have attached a super rough sketch of what i am thinking. i know there will be an expansion tank and maybe a mixing valve and pumps and what not but this sketch is just confirming what you mean when you say your have one continuous coil that runs thru the storage and then onto the emitter. so when there is a fire building btu it is running thru the tank and heating the tank and the emitter at the same time and when no fire it is just running thru the whole system but pulling energy from the tank. correct?

 

[hobbyheater]

Have you tried Smokeless Heat for tanks that will go through doors, Expensive yes but no big mess from a failed liner !
(broken link removed)

 

[peakbagger]

It has been awhile since I had this out but this is my system with oil backup. Its uses a TACO system controller to run the zones. If the wood boiler power is turned off or the temp in the wood boiler drops below 140F the oil boiler runs normally otherwise its locked out and the automated isolation valves route the water around the oil boiler. The storage pump with an integral flow check (IFC) was taken out and replaced with check valve as it was not needed.

Note, I do not have thermovar on this system to keep the return water hot to the boiler, its an old burnham wood/coal unit that really would not benefit from one the way I run it. It oulw be easy to add and suggest you do.

I am in the process of replacing the backup oil boiler with a "cold start" type as my old cast iron one has finally started leaking as it was not designed for this type of use (I still got 20 years off it). I plan to install a hydraulic separator to isolate the oil boiler from the wood boiler as I do have some minor "ghost flow" issues.

BTW, some of the lines that look like they connect do not. This was definitely a working drawing. The control logic looks complex as I did not want to use a PLC so its all relay logic.

 

[nbrouse]

Have you tried Smokeless Heat for tanks that will go through doors, Expensive yes but no big mess from a failed liner !
(broken link removed)

those look great but quite out of my budget at the moment.

 

[nbrouse]

It has been awhile since I had this out but this is my system with oil backup. Its uses a TACO system controller to run the zones. If the wood boiler power is turned off or the temp in the wood boiler drops below 140F the oil boiler runs normally otherwise its locked out and the automated isolation valves route the water around the oil boiler. The storage pump with an integral flow check (IFC) was taken out and replaced with check valve as it was not needed.

Note, I do not have thermovar on this system to keep the return water hot to the boiler, its an old burnham wood/coal unit that really would not benefit from one the way I run it. It oulw be easy to add and suggest you do.

I am in the process of replacing the backup oil boiler with a "cold start" type as my old cast iron one has finally started leaking as it was not designed for this type of use (I still got 20 years off it). I plan to install a hydraulic separator to isolate the oil boiler from the wood boiler as I do have some minor "ghost flow" issues.

BTW, some of the lines that look like they connect do not. This was definitely a working drawing. The control logic looks complex as I did not want to use a PLC so its all relay logic.


View attachment 317755

wow thats alot for a simpleton like me to take in. my system will be much simpler (i hope) its really just one boiler and one emitter. my biggest question is can i just run one continuous coil thru the storage from boiler to the emitter?

 

[nbrouse]

@peakbagger here is an illustration i found that more closely represents my set up in simplicity. the main difference here is that the storage tank shown is pressurized. imagine for it as nonpressurized with a hx coil running thru it.

question 1. i run a tube style hx thru the tank coming from the boiler. being that the tank is 4 foot tall do it place the coil at the top, bottom or have it travel through both the height of the whole thing.

question 2 on the return side should i run the return back thru the storage tank or bypass the tank and run it to the boiler?

i am sorry for so many questions that probably seem simple to you guys im just trying to wrap my head around this and get a good undestanding of it.

another question regarding the mixing valve. is the purpose of the mixing valve to add temp back into the return side? is that needed with only a water to air hx?

this is where i wonder to myself if it would be more efficient for the purpose of retaining btu's to have 2 seperate loops. one closed loop with a coil and its own pump and expansion tank on the boiler side. it comes off the boiler, into the storage tank heating the water in the tank. back out into the boiler. this loops sole purpose would be to heat the storage water. the pump on this side would only run when it the boiler is building energy to add it to the storage.

another loop would be on the emitter side. a 2nd coil that drops into the storage tank with a pump and expansion tank of its own. when the thermostat calls for heat this pump turns on and starts cycling hot water thru the emitter. when the thermostat is satisfied it stops pumping and pulling energy from the storage.

for simplicity at this point my emitter is only going to be the air to water hx put into the plenum of my heat pumps air handler so i do not need to constantly circulate water thru it like a radiator or baseboard emitter. i am not sure what temperature my heat pump emitter works at but when my heat kicks on it rarely runs more than a minute or 2 to maintain the temp. the only time it runs longer than that is say in the morning when the t-stat bumps it back up from the over night setting of 65 to the day time setting of 70. then it will run for maybe 5 minutes straight to satisfy that need.

does this make sense? am i just rambling? lol im sorry. i find text conversations difficult. im better face to face or over a phone.

 

[maple1]

Are you sure you couldn't use smaller LP tanks plumbed together? Say, 6x 100 gallons, for example?

 

[nbrouse]

Are you sure you couldn't use smaller LP tanks plumbed together? Say, 6x 100 gallons, for example?

Those 100 gallon are 36 diameter id have to double check. I may be able to squeeze them in but theyre also not that cheap. Im seeing 250 a pc around here

 

[all night moe]

Those 100 gallon are 36 diameter id have to double check. I may be able to squeeze them in but theyre also not that cheap. Im seeing 250 a pc around here

I would love to find a 120ga, aka 420lb, lp tank for 250.